U.S. patent application number 13/693038 was filed with the patent office on 2013-06-06 for electrically rechargeable, dual chemistry, battery system for use in plug-in or hybrid electric vehicles.
The applicant listed for this patent is Elton J. CAIRNS, Nad KARIM, Paul H. VROOMEN. Invention is credited to Elton J. CAIRNS, Nad KARIM, Paul H. VROOMEN.
Application Number | 20130141045 13/693038 |
Document ID | / |
Family ID | 48523503 |
Filed Date | 2013-06-06 |
United States Patent
Application |
20130141045 |
Kind Code |
A1 |
KARIM; Nad ; et al. |
June 6, 2013 |
ELECTRICALLY RECHARGEABLE, DUAL CHEMISTRY, BATTERY SYSTEM FOR USE
IN PLUG-IN OR HYBRID ELECTRIC VEHICLES
Abstract
An apparatus, method and system are disclosed, relating to a
dual-chemistry battery subsystem having different battery
chemistries and performance properties, and relating to an
algorithm of charging and discharging the battery subsystem. For an
EV application, the battery subsystem is a tailored solution that
combines two different battery configurations, a first battery
configuration and a second battery configuration, to satisfy the
unique needs of different driving modes and performance profiles of
an EV, such as a typical workday commute versus an occasional
extended range trip on the weekend. The present disclosure provides
intelligent control and heuristics to maximize useful energy on a
wide variety of battery applications.
Inventors: |
KARIM; Nad; (Palo Alto,
CA) ; CAIRNS; Elton J.; (Walnut Creek, CA) ;
VROOMEN; Paul H.; (Santa Cruz, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KARIM; Nad
CAIRNS; Elton J.
VROOMEN; Paul H. |
Palo Alto
Walnut Creek
Santa Cruz |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
48523503 |
Appl. No.: |
13/693038 |
Filed: |
December 3, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61566143 |
Dec 2, 2011 |
|
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|
61720484 |
Oct 31, 2012 |
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Current U.S.
Class: |
320/110 ;
307/10.1; 320/128 |
Current CPC
Class: |
H02J 7/0042 20130101;
Y02T 10/70 20130101; H02J 7/342 20200101; H02J 2310/48 20200101;
H02J 7/0068 20130101; Y02T 90/14 20130101; B60L 58/20 20190201;
B60L 58/12 20190201; Y02E 60/10 20130101; H02J 7/0069 20200101 |
Class at
Publication: |
320/110 ;
320/128; 307/10.1 |
International
Class: |
H02J 7/00 20060101
H02J007/00; B60L 11/18 20060101 B60L011/18 |
Claims
1. A battery subsystem comprising: a main battery pack having a
cycle rating for a given quantity of cycles over a useful life; a
supplemental battery pack having a cycle rating for a given
quantity of cycles over a useful life; a switch coupled to both the
main battery pack and the supplemental battery pack, wherein the
switch selectively couples the main battery pack or the
supplemental battery pack to an electrical load or to an electrical
energy source; wherein the cycle rating of the main battery pack is
substantially greater than the cycle rating of the supplemental
battery pack; and wherein the switch is configured to discharge or
charge the main battery pack preferentially over the supplemental
battery pack.
2. The battery subsystem of claim 1 wherein: the main battery pack
is configured such that the given quantity of cycles for the useful
life of at least 3,000 cycles; and the useful life is a cycle
rating of a quantity of cycles over which an energy capacity of the
battery is equal to or greater than approximately 80 percent of an
original capacity of the battery.
3. The battery subsystem of claim 1 wherein: the cycle rating of
the main battery pack divided by the cycle rating of the
supplemental battery pack results in a cycling ratio; and the
cycling ratio is equal to or greater than approximately two.
4. The battery subsystem of claim 1 wherein: the main battery pack
and the supplemental battery pack are both configurable to be fully
dischargeable to an approximately zero state of charge.
5. The battery subsystem of claim 2 wherein: the main battery pack
comprises a plurality of cells coupled to each other, wherein each
of the cells of the main battery pack has a chemistry and
construction with a characteristic impedance; the supplemental
battery pack comprises a plurality of cells coupled to each other,
wherein each of the cells of the supplemental battery pack has a
chemistry and construction with a characteristic impedance; and the
characteristic impedance of each of the cells in the main battery
pack is lower than the characteristic impedance of each of the
cells in the supplemental battery pack.
6. The battery subsystem of claim 5 wherein: the characteristic
impedance of the cells in the main battery pack divided by the
characteristic impedance of the cells in the supplemental battery
pack results in an impedance ratio; and the impedance ratio is
equal to or less than approximately 0.5.
7. The battery subsystem of claim 1 wherein: the main battery pack
has an energy rating; the supplemental battery pack has an energy
rating; the energy rating of the supplemental battery pack divided
by the energy rating of the main battery pack results in an energy
ratio; and the energy ratio is configured to be equal to or greater
than 2.
8. The battery subsystem of claim 7 wherein: the main battery pack
has a maximum C rate; the supplemental battery pack has a maximum C
rate; wherein the maximum C rate of the main battery pack is
greater than the maximum C rate of the supplemental battery
pack.
9. The battery subsystem of claim 1 wherein: the main battery pack
is comprised of a lithium titanium oxide (Li2TiO3) cell; or the
supplemental battery pack is comprised of a lithium cobalt oxide
(LiCoO2) cell.
10. The battery subsystem of claim 5 wherein: the main battery pack
and the supplemental battery pack have a combined weight that is at
least approximately 25% less than a weight of a single battery
designed with the chemistry and construction of either the main or
supplemental battery pack and with an energy capacity similar to
the battery subsystem and a similar cycle rating as the main
battery pack.
11. A method of cycling a battery subsystem having a main battery
pack and a supplemental battery pack selectively coupled to an
electrical load by a switch, the method comprising: discharging the
main battery pack, which has a cycle rating for a quantity of
cycles over a useful life, preferentially before discharging the
supplemental battery pack, which has a cycle rating for a quantity
of cycles over a useful life; charging the main battery pack
preferentially before charging the supplemental battery pack; and
wherein: the useful life of the main battery pack is equivalent to
an EV driving life of at least 100,000 miles; the main battery pack
is comprised of a plurality of cells having a chemistry type; the
supplementary battery pack is comprised of a plurality of cells
having a chemistry type; and the chemistry type of the main battery
pack is different from the chemistry type of the supplemental
battery pack.
12. The method of claim 11 wherein preferentially charging the main
battery pack occurs if the state of charge of the main battery pack
is less than a full charge, regardless of the state of the
supplemental battery pack.
13. The method of claim 11 wherein: the main battery has a battery
design rating; the supplemental battery has a battery design
rating; the battery design rating of the main battery is different
than the battery design rating of the supplemental battery; and the
battery design rating is a thermal profile rating, a cell impedance
rating, an energy density rating, or a cycle rating.
14. The method of claim 13 wherein: the main battery pack has a
cycle rating that is greater than a cycle rating of the
supplemental battery pack.
15. The method of claim 11 further comprising: discharging the main
battery pack and the second battery pack sequentially.
16. The method of claim 15 further comprising: selecting a
discharge percentage for the main battery pack in a range of 50 to
90 percent; and discharging the main battery pack to the selected
discharge percentage prior to starting to discharge the
supplemental battery
17. The method of claim 11 further comprising: selectively
discharging the main battery pack and the supplemental battery pack
sequentially or parallely with respect to each other, depending
upon the mode of battery consumption detected.
18. The method of claim 11 further comprising: preferentially
charging the main battery pack from a regenerative energy source
before recharging the supplemental battery pack from the
regenerative energy source.
19. The method of claim 11 further comprising: discharging the main
battery pack to an approximately depleted state; then discharging
the supplemental battery pack; and charging the main battery pack
via a regenerative energy source preferentially over the
supplemental battery pack; and repeating the discharging of the
main battery pack to between 50-95 percent of an original capacity
prior to repeating the discharging of the supplemental battery
pack.
20. The method of claim 11 further comprising: fully discharging
the main battery pack to an approximately zero charge; and then
fully discharging the supplemental battery pack to an approximately
zero charge.
21. The method of claim 11 further comprising: discharging the main
battery pack more frequently than the supplemental battery
pack.
22. The method of claim 11 further comprising: configuring the main
battery pack to be fully dischargeable to an approximately zero
charge a number of times over its useful life approximately equal
to a cycle rating of the main battery pack; configuring the
supplemental battery pack to be fully dischargeable to an
approximately zero charge a number of times over its useful life
approximately equal to a cycle rating of the supplemental battery
pack; and wherein: the number of times the main battery pack is
fully dischargeable divided by the number of times the supplemental
battery pack is fully dischargeable results in a discharge ratio
that is approximately equal to a cycling ratio; and the useful life
of the main battery pack and the useful life of the supplemental
battery pack are equivalent to an EV driving life of at least
100,000 miles.
23. The method of claim 13 further comprising: configuring the main
battery pack and the supplemental battery pack to be fully
dischargeable while maintaining a lifetime cycling of the battery
subsystem of approximately equivalent to an EV driving life of at
least 100,000 miles.
24. An energy management system comprising: an electric load; an
electrical energy source; a battery subsystem coupled to the
electric load and the electrical power source; a battery management
system (BMS) coupled to the battery subsystem, wherein the BMS
includes a microcontroller configured to implement an algorithm for
charging and discharging the main battery pack and the supplemental
battery pack; and a temperature management system (TMS) coupled to
the battery subsystem, wherein the TMS includes a microcontroller
configured to implement an algorithm for charging and discharging
the main battery pack and the supplemental battery pack; and
wherein the battery system comprises: a main battery pack having a
cycle rating for a given quantity of cycles; a supplemental battery
pack having a cycle rating for a given quantity of cycles; a switch
coupled to both the main battery pack and the supplemental battery
pack, wherein the switch selectively couples the main battery pack
or the supplemental battery pack to an electrical load or to an
electrical energy source; and wherein: the cycle rating of the main
battery pack is substantially greater than the cycle rating of the
supplemental battery pack; and the switch is configured to
discharge the main battery pack preferentially over the
supplemental battery pack.
25. The energy management system of claim 24 wherein: the
electrical load is an electric motor in an electric vehicle (EV);
and the TMS comprises: a cooling/heating system for the main
battery pack; and a cooling/heating system for the supplemental
battery pack; and the heating/cooling system for the main battery
pack is independent and different from the cooling system used for
the supplemental battery pack.
26. The energy management system of claim 25 wherein: the cooling
system of the main battery pack is a passive air cooled system; and
the cooling system of the supplemental battery pack is an active
liquid cooled system.
27. The energy management system of claim 25 wherein the main
battery pack has a power and an energy capacity sufficient to
provide approximately all the performance needed for a nominal
commuting profile such that no more than approximately 20% of the
energy from the supplemental battery pack is needed.
28. The energy management system of claim 28 wherein the
supplemental battery pack is sized for an energy capacity
sufficient for an extended driving profile, wherein the extended
driving profile begins after exercising the nominal commuting
profile up to a maximum driving range.
29. The energy management system of claim 28 wherein: the battery
subsystem has a combined weight equal to a weight of the main
battery pack plus a weight of the supplemental battery pack; the
battery subsystem has a sufficient cycle rating to provide a
projected lifetime of at least 100,000 EV miles at the nominal
commuting profile and the extended driving profile; and the weight
of the battery subsystem is at least approximately 25 percent less
than a weight of a single battery design, subsystem having a
homogeneous chemistry of either the main or supplemental battery
pack, with sufficient cycle rating to provide the projected
lifetime of driving cycles of the EV at the given commuting profile
and the extended driving profile, corresponding to at least 100,000
miles.
30. The energy management system of claim 24 wherein the BMS is
configured to recharge the main battery pack from regenerative
power, preferentially or exclusively, with respect to the
supplemental battery pack.
31. The battery subsystem system of claim 25 wherein: the main
battery pack and the supplemental battery pack are both configured
to be fully dischargeable; and the main battery pack and the
supplemental battery pack provide a lifetime usage of 100,000 miles
of nominal EV driving schedules.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to provisional
application(s): Ser. No. 61/566,143 filed Dec. 2, 2011, entitled
"Electrically rechargeable, dual chemistry, battery system for use
in plug-in electric vehicles or hybrid electric vehicles; Ser. No.
61/720,484, filed Oct. 31, 2012, also entitled "ELECTRICALLY
RECHARGEABLE, DUAL CHEMISTRY, BATTERY SYSTEM FOR USE IN PLUG-IN
ELECTRIC VEHICLES OR HYBRID ELECTRIC VEHICLES," which applications
are also incorporated by reference herein in their entirety.
FIELD OF TECHNOLOGY
[0002] This disclosure relates generally to the technical field of
electrical charging and discharging, and in one example embodiment,
this disclosure relates to a method, apparatus and system of
batteries.
BACKGROUND
[0003] Batteries are used to store and release energy in either a
slow or a quick manner depending on the needs. Wide varieties of
applications utilize batteries including mobile and stationary,
vehicular and non-vehicular systems.
[0004] Batteries can have many different performance, or design,
ratings to assist a user in matching the battery to an application.
The application's need may be in terms of power (rate), total
energy (capacity), quantity of cycling, depth of cycling, thermal
characteristics, impedance, etc. or some combination of these
design ratings. There are nearly always tradeoffs between the
different choices of design ratings. For example, a long cycle life
battery is typically costly and heavy. A high-volume consumer type
battery can be inexpensive, but is typically neither high-power nor
high cycling. For an EV application, there may be different demands
on a battery performance that are not satisfied in a single given
design. For example, one battery design may provide sufficient
power for acceleration needs, but insufficient energy for extended
use. While a combination of a high-energy battery with a high-power
battery provides sufficient electrical resources for that single
scenario, as described in U.S. Pat. No. 7,049,792, entitled "Method
and apparatus for a hybrid battery configuration for use in an
electric or hybrid electric motive power system," there are a wide
variety of other applications and scenarios that are not satisfied
by that particular combination.
SUMMARY
[0005] An apparatus, method and system are disclosed, relating to a
multi-chemistry battery subsystem having different battery
chemistries and performance properties, and relating to an
algorithm of charging and discharging the battery subsystem. For an
EV application, the battery subsystem is a tailored solution that
combines two different battery configurations, a first battery
configuration and a second battery configuration, to satisfy the
unique needs of different driving modes and performance profiles of
an EV, such as a typical workday commute versus an occasional
extended range trip on the weekend. The present disclosure provides
intelligent control and heuristics to maximize useful energy on a
wide variety of battery applications including stationary
applications, such as load balancing and backup power,
mobile/terrestrial applications, such as hybrid electric vehicles
(series or parallel), plug-in electric vehicles (EVs) (e.g., cars,
bikes, trains, busses, etc.), and applications that are
mobile/airborne, such as aircraft and drones.
[0006] A first battery configuration, called the main battery pack
(MBP), is built from cells having beneficial properties of high
cycle rating and low impedance that are applied to the high-power
demands of accelerating from a stop and the high-cycle rate of stop
and go traffic that discharge the battery and then charge the
battery from regenerative braking. Because this first battery
configuration also has the undesirable properties of high-weight
and high-cost, the size of the first battery configuration is
tailored only large enough to satisfy the more frequently traveled,
nominal commute range of an EV, the portion of the EV's nominal
driving profile that would need those beneficial properties.
[0007] A second battery configuration, called the supplemental
battery pack (SBP), is built from cells having beneficial
properties of high specific-energy, and low-cost features that are
slated to power the less frequent demands of extended driving
beyond the nominal commute profile. Consequently, the second
battery configuration is designed as a larger size than the first
battery configuration because the higher energy output for extended
range driving. Because the second battery configuration is
comprised of lower specific power cells, it builds more cells in
parallel to satisfy the power need, thereby resulting in a larger
battery form factor. Thus, both the first battery pack and the
second battery pack are individually capable of providing the power
and energy required by the load. Lastly, because the second battery
configuration is made of a cell having a high impedance it
consequently generates more heat. Thus, the second battery
configuration is managed by a discharging and charging algorithm
that directs all possible battery cycling to the first battery
configuration, using the second battery configuration only when the
first battery configuration is inadequate or depleted. Thus, the
discharging and charging algorithm will rely primarily on
discharging and charging the first battery configuration, or main
battery pack, for the lion's share of the battery use and cycling
in an EV. The MBP and the SBP are configurable to discharge in
multiple different discharge modes based on their design tradeoffs
and their current state, as well as the system needs. The MBP and
the SBP typically operate in series or sequentially, that is one
after the other, with the main battery pack providing all or nearly
all the cycling until it has no charge remaining, because they both
have adequate power and energy for the load. However, the multiple
battery packs, MBP and SBP, can also operate in parallel for a less
often scenario where the SBP has a deficit condition and is
temporarily unable to supply the rated, or maximum needed current
by the load, e.g., the EV motor.
[0008] By using a multi-chemistry, e.g., dual chemistry, battery
subsystem that combines of the first and second battery
configurations and by tailoring the size of the first and second
battery configurations to the EV driving profile, several
significant benefits arise. The battery subsystem is cheaper,
lighter, and/or longer-lived than a theoretical equivalent single
battery design that would use the chemistry/construction of either
the first battery configuration or the second battery
configuration. In particular, the lifespan of the second battery
configuration is preserved by utilizing the second battery
configuration only when the first battery configuration is
essentially depleted. Fewer cycles on the second battery
configuration translates into longer life, thus compensating for
its substantially lower cycle rating when compared to the first
battery configuration. The MBP, while called main, is not
necessarily given that term because of its physical size or its
capacity, because in the present embodiment the MBP is actually
physically smaller and lower capacity than the SBP. Rather, the MBP
is called this because it is the primary, e.g. first, battery that
is discharged, if it has any state of charge, and it is the primary
battery that is charged, if it has less than a full state of
charge. In another embodiment, the physical size and the capacity
of the MBP could be larger than the SBP, but the MBP would still be
the primary battery that is discharged, if it has any state of
charge, and it is the primary battery that is charged, if it has
less than a full state of charge. The SBP is charged only if the
MBP has no charge, or has reached a threshold SoC.
[0009] As a comparison, if a theoretical single battery design were
to utilize only the heavy but high-cycling first battery chemistry
and construction to supply all the needs of the EV, a large portion
of battery's high-cycling performance capability would be an
overdesign for the infrequent extended range driving needs.
Resultantly, a large portion of the single battery design would
unnecessarily be using the low specific energy and the high cost of
that first battery configuration, which would thusly detract from
that solution.
[0010] Conversely, if an alternative theoretical single battery
design were to utilize only the low cycling and low-life but
high-energy second battery configuration to supply all the needs of
the EV, it would have to be overdesigned in capacity to compensate
for the low cycling, low-depth of discharge, and low power rating
that it exhibits. That is, the single battery of the second battery
configuration would have to be restricted in its depth of
discharge, e.g., only to 70%, in order to avoid the low-life
behavior at full depth of discharge. Thus 30% of the battery would
never be usable, resulting in a life-long weight penalty to the EV
of 30% of the battery weight. Similarly, the low-power aspect of
the second battery configuration would require the single battery
design to be oversized to provide the desired power, again
resulting in an increase in size and weight.
[0011] Other features and advantages of the present disclosure will
be apparent to those of ordinary skill in the art from the
accompanying drawings and from the detailed description of the
preferred embodiments that follows. Accordingly, the specification
and drawings are to be regarded in an illustrative rather than a
restrictive sense.
BRIEF DESCRIPTION OF THE VIEW OF DRAWINGS
[0012] Example embodiments are illustrated by way of example and
not limitation in the figures of the accompanying drawings, in
which like references indicate similar elements and in which:
[0013] FIG. 1 is a functional block diagram of a battery subsystem
having two different types of batteries that are tailored to two
different roles in an electric vehicle (EV), according to one or
more embodiments.
[0014] FIG. 2 is a block diagram of an energy management system for
an EV using two different types of batteries, according to one or
more embodiments.
[0015] FIG. 3A is a graph illustrating a relationship between an EV
driving ratio and an energy ratio of a supplemental to main battery
in a battery subsystem, according to one or more embodiments.
[0016] FIG. 3B is a graph illustrating a percentage of trips vs. a
given range, for an exemplary short-commute/occasional extended
driving pattern along with a resultant coverage provided by
tailoring the main and supplemental battery pack to the driving
pattern, respectively, according to one or more embodiments.
[0017] FIG. 3C is a graph illustrating a percentage of trips vs. a
given range, for an exemplary long-commute/occasional extended
driving pattern along with a resultant coverage provided by
tailoring the main and supplemental battery pack to the driving
pattern, respectively, according to one or more embodiments.
[0018] FIG. 4A is a time vs. state of charge (SoC) graph of the
main and supplemental battery packs for a hypothetical single-trip
driving scenario that discharges and regeneratively recharges only
the main battery pack, according to one or more embodiments.
[0019] FIG. 4B is a time vs. state of charge (SoC) graph of the
main and supplemental battery packs for a hypothetical single-trip
driving scenario that discharges the main battery pack to a fully
discharged state first, and then drives the supplemental pack to a
fully discharged state, according to one or more embodiments.
[0020] FIG. 4C is a time vs. state of charge (SoC) graph of the
main and supplemental battery packs for a hypothetical single-trip
driving scenario that only discharges the main battery pack to a
threshold state of charge to retain a reserve capacity in the main
battery pack that can compensate for a power deficit in the
supplemental battery pack, according to one or more
embodiments.
[0021] FIG. 5 is a graph illustrating a range of the ratios of
design parameters for the main battery pack to those of the
supplemental battery pack, respectively, on log-linear axes,
according to one or more embodiments.
[0022] FIG. 6A is a flowchart of a method for discharging a main
battery pack to a fully discharged state prior to starting to
discharge a supplemental battery pack to a fully discharged state,
according to one or more embodiments.
[0023] FIG. 6B is a flowchart of a method for discharging a main
battery pack to a reserve capacity state prior to starting to
discharge a supplemental battery, such that the main battery pack
can compensate for a power deficit in the supplemental battery
pack, according to one or more embodiments.
[0024] FIG. 6C is a flowchart of a method for regeneratively
charging a main battery pack to a fully charged state prior to
starting to regeneratively charge a supplemental battery pack to a
fully charged state, according to one or more embodiments.
[0025] Other features of the present embodiments will be apparent
from the accompanying drawings and from the detailed description
that follows.
DETAILED DESCRIPTION
[0026] An apparatus, method and system that provides a dual
chemistry battery (DCB) module having at least two different
battery packs, with each having different battery chemistries and
performance properties, and provides an algorithm of charging and
discharging the battery subsystem is disclosed. For an EV
application, the battery subsystem is a tailored solution that
combines two different battery configurations, a first battery
configuration and a second battery configuration to satisfy the
unique needs of each of the two primary driving modes and
performance profiles of an EV. In the following description, for
the purposes of explanation, numerous specific details are set
forth in order to provide a thorough understanding of the various
embodiments. It will be evident, however to one skilled in the art
that various embodiments may be practiced without these specific
details.
Functional Block Diagram
[0027] Referring now to FIG. 1, a functional block diagram of a
battery subsystem 100 having two different types of traction
batteries that are tailored respectively to two different roles in
an electric vehicle (EV) is shown, according to one or more
embodiments. The battery subsystem 100 is comprised of at least two
different battery packs having different chemistry and/or
construction types that provide distinctive tradeoffs to each other
in terms of battery design ratings and properties. These tradeoffs
can be tailored to a given application's needs in a manner that
results in a tuned system with improved performance, lower weight,
improved reliability, improved safety, and/or lower cost than a
battery system that provides an essentially homogenous single-type
of battery construction. In the present embodiment, the battery
subsystem 100 has a main battery 10 that has a type #1 of
construction and chemistry that provides one or more of the
following properties in a wide variety of combinations: high cycle
rating; low impedance; fast charging; thermally stable; high
specific power. The present embodiment also provides supplemental
battery pack 30 that has a type #2 of construction and chemistry
that provides one or more of the following properties in many
possible combinations: low cycle rating, high impedance, slow
charging, high specific energy, and/or low cost. In one embodiment,
all the battery design ratings shown apply to the respective type
of battery shown, with type #1 main battery 10, e.g., MBP, being a
lithium titanate oxide (LiTi2O3, or LTO) battery, and type #2
supplemental battery 30, e.g., SBP, being a lithium cobalt oxide
(LiCoO2) battery. However, a wide range of battery types can be
applied to the module with segregated battery pack tailoring as
shown. Battery management function 20, arbitrates between the two
sources of power, to decide when either of the batteries will
provide the load, based on their design tradeoffs and their current
state, as well as the system needs.
[0028] In the present embodiment, main battery 10 is tailored for a
function 10-A of a nominal commute profile with additional specific
exemplary functions such as: function 10-B wherein all discharges
initiate form the main battery (BTTY) if the main battery is not
fully charged, e.g., if the main battery has a state of charge
(SoC) that is greater than approximately zero percent (0%); and
such as function 10-C wherein all regenerative (REGEN) charges
initiate to the main battery if the main battery is not
approximately fully charged, e.g. if the main battery has a SoC
that is less than approximately one-hundred percent (100%). In
addition supplemental battery 30 is tailored for a function 30-A of
an extended driving profile. That is, main battery 10 is a high
cycle rating, low impedance, thermally stable battery that makes it
a long lasting and naturally durable good for the EV in comparison
to the supplemental battery with its low cycle rating, high
impedance, and low cost, e.g., low cost/kWh, making it a
replaceable wear out part. The following figures and descriptions
provide the qualitative and quantitative standards for tailoring
which of the different battery types will apply to which of the
different loads and applications in an energy management system,
e.g., an EV, and the ratio of capacity of the different battery
types that results in a tuned system with improved performance,
lower weight, improved reliability and longevity, improved safety,
and/or lower cost.
Architecture
[0029] Referring now to FIG. 2, a block diagram of an energy
management system 200 for an EV using two different types of
traction batteries is shown, according to one or more embodiments.
The EV application can be a car, bike, motorcycle, aircraft, or any
other mobile application where cost, weight, and/or reliability and
longevity are factors to consider in the design of a battery
system. Energy management system is also applicable to other
non-mobile applications such as load balancing systems, etc.
[0030] Battery subsystem 230 includes a main battery pack (MBP) 240
and a supplemental battery pack (SBP) 250 coupled in parallel to a
switch 232 that is itself coupled to a motor/generator 270. In the
present embodiment, MBP 240 and SBP 250 are neither coupled to each
other nor transfer charge between each other per se, e.g., via
switch 232. Rather switch 232 is a power electronics device, such
as an insulated gate bi-polar junction transistor (BJT), thyristor,
silicon controlled rectifier (SCR), or the like, that is
configurable to switch an electrical connection between
motor/generator 270 and MBP 240 and/or SBP 250, as well as pulse
width modulate each of MBP 240 and/or SBP 250 for desired current
conducted between MBP 240 and SBP 250 and motor/generator 270,
e.g., either in a battery charge or a discharge mode. In one mode,
switch 232 is configured to provide a serial transfer of power from
MBP 240 or SBP 250 to motor/generator 270, while in another
embodiment, switch 232 provide parallel coupling of MBP 240 and SBP
250 to motor/generator 270 for a parallel transfer of power.
[0031] Battery subsystem 230 is controlled by a battery management
system (BMS) 210, which has a memory 212, capable of storing data
and instructions, that is coupled to a microprocessor, or
microcontroller 214, that is capable of receiving input variables,
such as sensor data re: battery SoC and current rates, and then
execute instructions to enable an algorithmic control of the
discharging and charging of the MBP 240 and SBP 250, examples of
said algorithms being provided hereinafter in flowchart figures.
BMS 210 is coupled to motor/generator 270, battery subsystem 230,
TMS 220, and powertrain control module (PCM) 208 in order to
receive data and instructions and provide control of said
components, as appropriate to satisfy the functionality of the
energy management system 200.
[0032] A thermal management system (TMS) 220 is coupled to a
thermal control system for main battery pack (TCS-MAIN) 241 and to
thermal control system for supplemental battery pack (TCS-SUPPL)
251, which are in turn, coupled to MBP 240 and SBP 250,
respectively. The TCS-MAIN 241 and TCS-SUPPL 251 are a
heating/cooling system to bring the MBP and SBP to a temperature at
which they can provide sufficient current safely. TMS 220 also has
a memory 222, capable of storing data and instructions, that is
coupled to a microprocessor, or microcontroller 224, that is
capable of receiving input variables, such as sensor data re:
battery and system temperatures, and then execute instructions to
control TCS-MAIN 241 and/or TCS-SUPPL 251 to maintain safe
temperatures and prevent thermal runaway of MBP 240 and/or SBP 250,
though SBP 250 is the battery design more likely to have a thermal
issue, because it may be less stable and has relatively high
impedance.
[0033] The TCS-SPPL 251 and TCS-MAIN 241 are independently operated
in the present embodiment, are autonomous from each other, but are
controlled commonly by TMS 220. In one embodiment, TCS-MAIN 241 is
an air cooled passive system with at least one temperature sensor
that reads the temperature of MBP 240 in one or more locations and
communicates sensor information to the TMS 220. In the same
embodiment, TCS-SUPP 251 is a liquid cooled active system with at
least one temperature sensor that reads the temperature of SBP 250
in one or more locations and communicates sensor information to the
TMS 220. In turn, TMS 220 is coupled to BMS 210 to provide
temperature input in case of an over temperature situation which
would allow the BMS to reduce or cease discharging or charging to
MBP 240 or SBP 250. TCS-MAIN 241 is air cooled because it is
sufficiently safe for MBP 240 that is designed with a low impedance
and thermally stable battery cell design. TCS-SUPP 251 is water
cooled because SBP 250 is designed with a high-impedance, thermally
less stable battery cell that requires a larger capacity cooling to
keep it safe from a thermal runaway condition. Thus, the present
system 200 uses a dual cooling system (DCS) that complements the
needs of the DCB configuration. Control and sensing lines are shown
as dashed lines, the power transfer lines are shown as sold lines,
and cooling lines are shown as double lines. PCM 208 provides an
interface with the powertrain needs, the user input, such as
throttle position, etc., as well as the controller area network bus
(CAN bus) interaction and communication with other vehicular
systems.
[0034] In an alternative configuration, MBP 240 can be designed for
thermodynamics (DFTh) by having the cool and low impedance battery
located in the middle of the battery subsystem 230, with the
minimal amount of exposed surface area, and surrounded by the SBP
250 which would then have the maximum amount of surface area as the
circumferentially-located batteries in the battery subsystem 230.
This is an acceptable configuration to the extent that the SBP 250
is controlled during charge and discharge, as well as with the
TCS-SUPPL 251 to prevent overheating of the MBP 240, which may be
the more expensive component of the battery subsystem 230.
Ratios of Main to Supplemental Battery Packs
[0035] Referring now to FIG. 3A, a graph 300-A illustrating a
relationship between an EV driving ratio and an EV energy ratio of
a supplemental to main battery in a battery subsystem is shown,
according to one or more embodiments. The independent variable on
the horizontal axis is a qualitative dimensionless driving ratio,
ranging from low to high, which is equal to an extended driving
profile divided by a commuting profile. The dependant variable on
the vertical axis is a qualitative dimensionless energy ratio, also
ranging from low to high, which is equal to the energy rating of
the supplemental battery pack divided by the energy rating of the
main battery pack. As an example, a low point L represents a low
driving ratio, meaning that for this particular scenario either the
extended driving profile is low, e.g., it does not make up a high
percentage of the trips made by the EV, or the commute profile is
high, e.g. the EV makes a high percentage of trips that are short
commute trips, or both. The corresponding best DCB module for point
L driving ratio would be a low energy ratio DCB module, with a
supplemental battery having a lower energy rating than a main
battery. In other words, the DCB module would be high cycling
focused because of the driving profile. While this point defines
the relationship between the MBP and the SBP, the actual
quantitative values of the MBP and SBP would depend upon a given EV
weight, and the average and peak commute miles driven. From there
the size of SBP can be determined as the one remaining variable. A
similar analysis is performed for point H, which represents a
driving profile that has much higher percent of trips as extended
range as compared to the short-distance commute cycle.
[0036] In lieu of a customized DCB module for each discrete user,
several main demographic clusters of driving profiles can provide
several EV variants that cater to the given profiles, e.g., the
short-commuter, the mixed commuter-extended, and the long-range.
This arrangement would allow a user to purchase a vehicle that is
more closely tailored to their driving profile. The EV model would
be designed with a common floorpan for the multiple variants to fit
batteries with different ratios, and allow a user to swap-out the
DCB pack if a change in the driving profile arises.
Driving Scenarios
[0037] Referring now to FIG. 3B, a graph 300-B illustrating a
percentage of trips vs. a given range, for an exemplary
short-commute/occasional extended driving pattern along with a
resultant coverage provided by tailoring the main and supplemental
battery pack to the driving patterns, respectively is shown,
according to one or more embodiments. For both FIGS. 3B and 3C, the
horizontal axis represents the distance traveled in a given trip,
while the vertical axis represents the percentage (%) of trip made
at that given distance or greater. Point A in FIG. 3B indicates
that 80% of the trips made by the present driving profile have a
distance of 20 miles or more, while point B shows that 40% of the
trips have a distance of 30 miles or more, and finally point C
shows that only 20% of the trips are 50 miles or more. Stated
conversely, point B shows that 60% of the trips have a distance of
30 miles or less, an ideal profile for being the capacity target
for the MBP, with the balance of the extended range being sized for
the SBP.
[0038] Referring now to FIG. 3C, a graph 300-C illustrating a
percentage of trips versus a given range, for an exemplary
long-commute/occasional extended driving pattern along with a
resultant coverage provided by tailoring the main and supplemental
battery pack to the driving patterns, respectively is shown,
according to one or more embodiments. In comparison to FIG. 3B,
driving profile in FIG. 3C is clearly shifted to a having higher
percentages at a long range driving. Specifically, point D shows
that 80% of the trips are more than 30 miles, while point E shows
that 40% of the trips have a distance of 45 miles or more, and 20%
of the trips are 50 miles or more. Thus, points D and E are 50%
greater than the similar percentage points on FIG. 3B. If the
longer distances are related to less stop and go traffic, and thus
regen charging, providing a nominally sized MBP with high cycling
capability will reduce cost of the system, and avoid overdesigning
the high-cycling battery capacity.
Battery Charging/Discharging Scenarios
[0039] Referring now to FIG. 4A, a time vs. state of charge (SoC)
graph 400-A of the main and supplemental battery packs for a
hypothetical single-trip driving scenario that discharges and
regeneratively recharges only the main battery pack is shown,
according to one or more embodiments. SBP and MBP both have an
essentially fully charged condition at time T0. From T0 to T5, the
MBP is discharged, as shown by the negative slope curve, and
regeneratively charged, at intermittent bands, with the
regenerative curve having a positive slope. The driving finally
terminating at time T5 with an approximate 52% SoC prior to
receiving stationary charging of the MBP. During the nominal
duration of the nominal trip, the entire schedule of cycling was
absorbed by the MBP, which is designed to handle it. In contrast,
the SBP never received any discharge or charge, thus appearing as a
flat line at 100% SoC. Consequently, because the SBP has a lower
cycle rating, the SBP does not see any of its more limited
cycling-lifespan consumed, and thus it is preserved for the
potential of providing a discharge in a future extended range
scenario.
[0040] Referring now to FIG. 4B, a time vs. state of charge (SoC)
graph 400-B of the main and supplemental battery packs for a
hypothetical single-trip driving scenario that discharges the main
battery pack from a fully charged state to a fully discharged state
first, and then drives the supplemental pack from a fully charged
state to a fully discharged state is shown, according to one or
more embodiments. From time T0 to T6, all the cycling is absorbed
by the MBP until the SoC shows the MBP has finally been fully
consumed. Only at that point, does the SBP start discharging, shown
as a broken line because of the low discharge rate, at time T6,
from its fully charged state (100% SoC), through T7 where it
reaches an approximately 60% SoC, From T7 through T8, regenerative
charging opportunities are presented to the battery subsystem, but
those regen charging opportunities are all absorbed by MBP, per the
charging algorithm, because the MBP is below a full state of
charge. From T8 to T9, all the discharge comes from the SBP, shown
as a broken line because of the low discharge rate, because the MBP
is fully depleted. At time T9, the SBP is also fully depleted. Both
the SBP and the MBP enter a stationary charging operation, where
they can be charged in parallel as shown. Thus, the DCB system
allows for the full discharge of the MBP and the SBP in order to
benefit from propulsion provided by the total capacity of the
batteries. The lifespan operation of the SBP is maintained, even
though its cycle rating is a fraction of the MBP cycle rating,
because it is only cycled a fraction of the number of cycles the
MBP receives, e.g., since most of the MBP cycles represent those in
FIG. 4A. Thus, the EV with a DCB does not resultantly haul 30% of
battery capacity, like a low cycling rate single-chemistry battery
pack would, in order to maintain its expected life cycle through
100,000 miles of EV driving.
[0041] Referring now to FIG. 4C, a time vs. state of charge (SoC)
graph 400-C of the main and supplemental battery packs for a
hypothetical single-trip driving scenario that only discharges the
main battery pack to a threshold state of charge to retain a
reserve capacity in the main battery pack that can compensate for a
power deficit in the supplemental battery pack is shown, according
to one or more embodiments. Note that SBP SoC starts at 30% at time
T0, while MBP SoC at T0 is approximately 95%, thus illustrating
that MBP is prioritized to receive regen charging, and thus may
often times have a SoC that is higher than the SBP. From time T0 to
T11, MBP is discharged down to an optional threshold, "THm", which
is set arbitrarily at a default or a user-programmed reserve (RSV)
SoC. Beyond T11, MBP does not discharge because SBP can be
discharged without encountering a power deficit that would request
additional power from the MBP. However, at point T12, SBP does
encounter a power deficit, shown as point "PD" on the curve, and
thus does request MBP to provide assistance power, which
consequently drives MBP down to a totally discharged state at T13.
Beyond T13, SBP is solely discharged, shown as a broken line
because of the low discharge rate, as MBP is at a totally
discharged state. At T14, both MBP and SBP are fully discharged and
are subsequently charged back to a fully charged state in parallel.
A wide variety of power staggering algorithms can be implemented by
the MBP/SBP independent multi-battery pack architecture, for EV
driver needs, performance, and/or safety.
Span of Design Ratios for Main vs. Supplemental Battery Pack
[0042] Referring now to FIG. 5, a graph 500 illustrating a range of
the ratios of design parameters for the main battery pack to those
of the supplemental battery pack, respectively, on log-linear axes
is shown, according to one or more embodiments. The ratios shown
are applicable for exemplary battery chemistries of the present
embodiment of LiCoO2 and Li2TiO3. However, with the wide variation
of battery chemistries currently in existence and in development,
the choice of specific factors making up these ratios will change
as will the range of the ratios themselves. The graph 500 ordinate
is a logarithmic scale from 1 to 10 to 100. A solid line box
illustrates a first range of parameters, with an overlapping dashed
line box illustrating an optional range of parameters. Positive
design parameters are shown in a white box, with negative design
parameters shown in a line-patterned box. Parameters on the top
half of the graph focus on strong factors of MBP vis-a-vis SBP,
while parameters on the bottom half of the graph focus on strong
factors of SBP vis-a-vis MBP. Vertical or horizontal alignment or
arrangement of ratio ranges does not necessarily indicate a
relationship, though one may exist as described below. Some
parameters have tradeoffs, or are related to, other parameters, but
this depends somewhat upon the uniqueness of the many battery
chemistries available. The closer the ratio is to a value of "1,"
the more similar the MBP to the SBP are, and the less of a
potential benefit obtained from tailoring the distinctness between
the MBP and SBP to a specific need on an EV. Risk factors can also
be multiplied times the ratio ranges, such as considering a failure
mode in a complicated active liquid cooling system, which could
lead to degradation of the batteries in the SBP, versus a passive
air-cooled system, that is very simple, robust, and reliable. As
battery designs evolve and solve design issues in some design
parameters, some of the ranges of a ratio for a given factor may
shrink, as a weak battery design might catch up to a good battery
design, while some of the ranges of a ratio might actually grow, as
a good battery design gets better and the weak battery design makes
no improvement. In other cases, new factors may arise in a formerly
matched design parameter as one battery making drastic
improvements,
[0043] Regarding specific ratio ranges, the listed cycling ratio
range 402 extends from about 2 to 10 in one embodiment, and from 10
to approximately 80 in another embodiment. In particular, a
specific battery chemistry in the present embodiment has an
approximate 10:1 to 64:1 ratio range, depending upon the
manufacturer and design nuances, with Li2TiO3 MBP having a cycling
rate of 3,000 to 16,000 cycles, and with LiCoO2 SBP having a
cycling rate of approximately 250 to 500 Future developments in
these battery chemistries may result in a change in the specific
range of the ratio. Cost ratio 408 ranges from approximately 3 to
10, depending upon the manufacturer and design, where higher
cycling ratio ranges tending to have a higher cost range as well.
Thermal management overhead range 410 has a partial relationship to
impedance 412, because higher impedances typically leading to
higher cell temperatures and less thermal stability. To compensate
for higher cell temperatures, thermal management overhead range 410
includes the extra cost, complexity, and potential failure modes of
a liquid cooled active management system, and the reduced specific
energy resulting from the added cooling infrastructure in the
battery pack. In the present embodiment, the active liquid cooling
system requirement for LiTi2O3 batteries reduces its specific
energy by 50%, while the passive cooling system for LiCoO2 only
reduces its specific energy by 25%. Impedance ratio range 412
extends from approximately 3 to over 100, which has a substantial
effect on the thermal stability. In exemplary DCB, the impedance
ratio is 1:120 for LiTi2O3 versus LiCoO2, respectively. The
impedance rating of a battery depends upon many factors such as
electrical conductivity, mass transfer rate, and chemical reaction.
Energy ratio range 414 spans from approximately 2 to 40 in the
present embodiment. Energy ratio range is tied to energy density,
with the latter also affected by the thermal management overhead
ratio range 410 and the need for a space consuming cooling system
for low thermal stability batteries. Charge rate ratio 416 has a
range that spans from approximately 1 to 10 in the present
embodiment, with an exemplary higher-end ratio of 5:1 for a LiTi2O3
maximum C rate of 10 compared to a LiCoO2 maximum C rate of 2. For
example, a LiTi2O3 can fast charge as quickly as six minutes in
some cases.
Flowcharts
[0044] Flowcharts in FIGS. 6A through 6C relate to prior figures as
follows. The processes described in FIGS. 6A through 6C utilize the
DCB architecture in FIG. 2 which can have a wide range of battery
design parameters ratios, as described in FIG. 5, for the MBP/SBP
multi-battery subsystem that are tailored, depending upon the
application needs such as EV driving schedule combinations, as
described in FIGS. 3A-3C and trip SoC graphs described in FIGS.
4A-4C. The operations, inquiries and instructions executed and
outputs generated in FIGS. 6A-6C are primarily executed by the
battery management system (BMS) 210, and secondarily by the thermal
management system (TMS) 220, with some interaction with the
powertrain control module (PCM). Operations in a given flowchart
with same numbers as other flowcharts utilize those descriptions in
the given flowchart. The discharging operations of flowchart 600-A
and 600-B flip back and forth with the regen charging operations of
flowchart 600-C as needed, depending on the driving scenario, as
illustrated in exemplary FIGS. 4B and 4C.
[0045] Referring now to FIG. 6A, a flowchart 600-A of a method for
discharging a main battery pack to a fully discharged state prior
to starting to discharge a supplemental battery pack to a fully
discharged state is shown, according to one or more embodiments.
The top half of flowchart 600-A, from operation 608 through 616,
are bracketed to the left of the figure and labeled as the
preferential discharging operations, while the subsequent
operations in the bottom half of flowchart 600-A, from operation
622 onwards, are bracketed to the left of the figure and labeled as
the follow-on discharging operations. Flowchart 600-A is applicable
to the exemplary driving profiles exhibited in FIGS. 4A and 4B,
e.g., with decreases in SoC shown as negative slopes, being
accomplished by discharge operations hereinafter.
[0046] The preferential discharging operations begin with operation
608 which inquires whether a load demand exists, and if not, will
standby 610 for the signal, e.g., as initiated from a throttle
position sensor. If a load demand exists, the main battery pack is
discharged by operation 614 as the preferred source of energy.
Preferential priority is an automatic default to closing a switch
between the MBP and the load in one embodiment, with a fully
depleted MBP being immediately apparent. In another embodiment,
preferential priority can be determined by a host of factors, the
most significant being that the MBP has any capacity, e.g., the
apparent state of charge (SoC) is above approximately 0%. Given the
fact, that there are some lag effects in discharging the batteries,
there may be residual capacity in the MBP that does not appear
after a hard prior discharge. However, the physics of mass flow
rate, the chemistry of Brownian motion and exo/endothermic
reactions and the thermodynamics of heat transfer from/to the
exo/endothermic reactions all have an effect on the behavior of the
batteries. Other priority factors could include temperature of the
MBP vs. the SBP, with a warmer battery in a cold winter climate
being prioritized as more capable of delivering a charge, past
cycling history of the MBP vs. the SBP, etc. Inquiry 616 determines
whether the main battery is fully discharged or not, based on input
615 of metrics and status of main battery, e.g., SoC, recent
history on capacity discharged, existing current rate, temperature
of battery, temperature of heat sink (ambient air), etc. A host of
algorithms based on specific battery chemistry and vehicle
operation can be used to assist decision-making operation 616.
[0047] Follow-on discharging operations will arise after the MBP is
apparently fully discharged per sensor readings. The follow-on
discharging operations begin with operation 622 that discharges the
supplemental battery pack (SBP) to the load. This discharge
continues until the load ceases, or until the SBP is fully
discharged. Even though the SBP is made of a cell that has low
specific power, it is designed in the battery pack so as to satisfy
the power demands of the load, e.g. the EV electric motor. Thus,
each of the multiple battery packs, e.g. the SBP and the MBP, are
capable of individually satisfying the power demand of the load,
e.g., the EV motor. In the present embodiment flowchart 600-A, the
batteries provide that power and energy to the load in sequence,
e.g., either the MBP is providing all the power and energy, or the
SBP is providing all the power and energy, but both battery packs
are not coupled in parallel to both provide power to the load.
Inquiry 624 determines whether SBP is fully discharged, based on
metrics input 623 from sensor(s) on SBP, e.g., state of charge and
temperature readings of battery and cooling system, which is much
more important in the SBP because of its higher impedance and
consequently higher heat generation. If the SBP is fully discharged
or approaching full discharge, operation 625 notices BMS with a
message of same. If SBP is not fully discharged and the load
remains, then operation 622 continues the discharge. The flowchart
returns back up to operation 608 to inquire whether there is a load
demand. With the split discharging methodology in flowchart 600-A,
as preferential discharging of the MBP and subsequent follow-on
discharging of the SBP, the concentration of cycling, e.g., from
nominal commute profile, is beneficially focused on the MBP that is
best designed for it, with only extended driving profiles causing a
fraction of the cycling to occur at the SBP in the vast majority of
driving scenarios. There are outlier cases that are not suitable
for any typical EV. One example is a driving profile with a
consistent commute of sufficient distance and no regeneration that
it discharges both the MBP and the SBP every trip, e.g., a
long-distance service vehicle, is not sustainable with the current
system. However, statistics indicate that the vast majority of
typical consumer drivers will benefit from the current DCB
architecture and discharge/charge algorithms with extended range
for a given comparable battery weight to prior systems, or with
reduced weight and/or cost for a DCB battery system
[0048] Referring now to FIG. 6B, a flowchart 600-B of a method for
discharging a main battery pack to a reserve capacity state prior
to starting to discharge a supplemental battery, such that the main
battery pack can compensate for a power deficit in the supplemental
battery pack is shown, according to one or more embodiments.
Flowchart 600-B is arranged similarly to flowchart 600-A regarding
the top half being preferential discharging operations and the
bottom half for follow-on discharging operations. Flowchart 600-B
is applicable to the exemplary driving profiles exhibited in FIG.
4C, which illustrate the MBP threshold, THm, and the reserve in the
MBP for assisting a potential deficit in SBP.
[0049] In contrast to FIG. 6A, flowchart 600-B uniquely utilizes a
decision point 617 of a threshold voltage or SoC of the MBP, for
transferring the discharge operation from the MBP to the SBP at
some point prior to the MBP being fully discharged. The purpose is
to retain a reserve capacity in the MBP for future use in
compensating the SBP when the SBP has a power deficit, e.g., the
current drawn by the load exceeds the capability of the SBP. This
goal of reserve capacity in the MBP is accomplished by ceasing to
discharge the MBP, at least temporarily, in operation 618 and by
then initiating the discharge from the SBP in operation 622. An
intermediate inquiry in operation 620 determines whether a power
deficit exists in the SBP, and if so, proceeds to operation 626 to
discharge the MBP in parallel with discharging the SBP in order to
supplement the SBP with additional current. With the MBP
discharging, operation 626 proceeds to inquiry 628, which
determines whether the main battery is fully discharged, with the
help of a metrics input similar to input 615, though not shown for
operation 628. If MBP is fully discharged per operation 628, then
discharge naturally ceases and operation 629 notices the BMS with a
message. With SBP discharging and possibly MBP discharging,
flowchart proceeds to inquiry 624 to determine whether the SBP is
fully discharged. If so, then BMS is noticed with message per
operation 625, and if not, then flowchart returns to load demand
inquiry 608. As an alternative to operation 624 having a threshold
of full discharge, it could have a supplemental threshold (THs),
similar to the MBP threshold, THm, that would cease discharging the
SBP and proceed to capture the balance of the MBP reserve, prior to
running the SBP to full discharge. Again, the general goal is to
discharge the MBP rather than discharging the SBP, and to always
discharge the MBP fully, prior to discharging the SBP fully,
because the MBP is designed and better-suited to cycling and to
fast charge and to high-power, low impedance discharge. Thus, if
the price for the MBP is already paid in terms of high-cost and
high-weight, then the MBP should be used as the energy and power
source mainstay.
[0050] Referring now to FIG. 6C, a flowchart 600-C of a method for
regeneratively (regen) charging a main battery pack to a fully
charged state prior to starting to regeneratively charge a
supplemental battery pack to a fully charged state is shown,
according to one or more embodiments. Flowchart 600-C is arranged
similarly to flowcharts 600-A and 600-B regarding the top half
being preferential operations and the bottom half for follow-on
operations, albeit for regen charging operations in the present
flowchart rather than for discharging operations in the former
flowcharts. Flowchart 600-C is applicable to the exemplary driving
profiles exhibited in FIGS. 4A-4C, e.g., with increases in SoC
shown as positive slopes, that are accomplished by regen charge
operations hereinafter.
[0051] Regen charging begins with inquiry 650 determining whether
regen power is available, and if not, then standing by 652 and
repeating the inquiry, e.g., via input from a throttle position
and/or brake pedal position sensor in an EV. If regen power is
available, then operation 654 preferentially charges the MBP.
During the charging, operation 656 inquires whether the main
battery pack has reached a threshold value of being fully charged,
using input metrics 655 from SoC and current sensors on the MBP.
Thresholds other than "fully charged" may be used for different
algorithms and applications depending on the battery design and
driving profile. If the MBP is not fully charged, then the inquiry
650, charging 654, and inquiry 656 continuously occur. If the MBP
is fully charged, then operation 658 inquires whether the SBP is
fully charged, using SoC and current sensors as metrics input 657.
If the SBP is fully charged, then operation 659 prevents charging,
with an optional message to the BMS that both the MBP and the SBP
are fully charged. If the SBP is not fully charged, then operation
660 charges the SBP. The process of checking for regen power,
checking status of batteries and selectively charging them
continues constantly, and with the frequent changes in driving
profiles, will respond as indicated in previous driving profile
figures.
[0052] Charging of MBP and SBP by stationary units is accomplished
via a wide variety of means ranging from slow to fast charging, and
using various processes, as know by those skilled in the art.
Because the SBP has a lower C rating, due to thermal issues, and a
larger energy capacity to charge as compared to the MBP, the MBP is
more likely to be a higher SoC from a short charging operation.
This scenario still accomplishes the goal of preferentially, or
always, charging the MBP fully over the SBP when possible, and
preferentially, or always, discharging the MBP over the SBP, when
possible.
Battery Subsystem and Method Implementation
[0053] Based on the architecture of FIG. 2, the battery size
tradeoffs for driving profiles of FIGS. 3A-3C, the example driving
scenarios discharges and charges of FIGS. 4A-4C, the battery design
parameter ratios of FIG. 5, and/or the flowchart processes of FIGS.
6A-6C, one embodiment of a battery subsystem includes: a main
battery pack having a cycle rating for a given quantity of cycles
over a useful life; a supplemental battery pack having a cycle
rating for a given quantity of cycles over a useful life; and a
switch coupled to both the main battery pack and the supplemental
battery pack. The switch selectively couples the main battery pack
or the supplemental battery pack to an electrical load or to an
electrical energy source. The cycle rating of the main battery pack
is substantially greater than the cycle rating of the supplemental
battery pack; and the switch is configured to discharge or charge
the main battery pack preferentially over the supplemental battery
pack. The main battery pack is configured such that the given
quantity of cycles for the useful life of at least approximately
1,000 or 1,500 or 3,000 cycles (depending upon the driving
profiles), and in one embodiment, 3,000 to 16,000 cycles; and the
useful life is a cycle rating of a quantity of cycles over which an
energy capacity of the battery is equal to or greater than
approximately 80 percent of an original capacity of the battery.
The cycle rating of the main battery pack divided by the cycle
rating of the supplemental battery pack results in a cycling ratio;
and the cycling ratio is equal to or greater than approximately two
(2), but can also be 2-5, 5-10, 10-20, and 20-100 in different
battery sizing and chemistry scenarios. The main battery pack and
the supplemental battery pack are both configurable to be fully
dischargeable to an approximately zero state of charge.
[0054] In one embodiment, the main battery pack comprises a
plurality of cells coupled to each other, wherein each of the cells
of the main battery pack has a chemistry and construction with
characteristic impedance; the supplemental battery pack comprises a
plurality of cells coupled to each other, wherein each of the cells
of the supplemental battery pack has a chemistry and construction
with a characteristic impedance; and the characteristic impedance
of each of the cells in the main battery pack is lower than the
characteristic impedance of each of the cells in the supplemental
battery pack. These characteristic impedance values can be
normalized for amp-hours to make a fair comparison. The
characteristic impedance of the cells in the main battery pack
divided by the characteristic impedance of the cells in the
supplemental battery pack results in an impedance ratio; and the
impedance ratio is equal to or less than approximately 0.5. The
main battery pack has an energy rating; the supplemental battery
pack has an energy rating; the energy rating of the supplemental
battery pack divided by the energy rating of the main battery pack
results in an energy ratio; and the energy ratio is configured to
be equal to or greater than 2. In other embodiments, the energy
ratio can be 2-5, 5-10, 10-100, or as needed for a driving profile
combined in different battery sizing and chemistry scenarios. The
main battery pack has a maximum C rate; the supplemental battery
pack has a maximum C rate; wherein the maximum C rate of the main
battery pack is greater than the maximum C rate of the supplemental
battery pack. In one embodiment the main battery pack is comprised
of a lithium titanium oxide (Li2TiO3) cell and in another
embodiment, the supplemental battery pack is comprised of lithium
cobalt (LiCoO2) cell. The main battery pack and the supplemental
battery pack have a combined weight that is at least approximately
25% less than a weight of a single battery designed with the
chemistry and construction of either the main or supplemental
battery pack and with an energy capacity similar to the battery
subsystem and a similar cycle rating as the main battery pack.
[0055] The battery subsystem above can be managed, in one
embodiment, by a method of discharging the main battery pack, which
has a cycle rating for a quantity of cycles over a useful life,
preferentially before discharging the supplemental battery pack,
which has a cycle rating for a quantity of cycles over a useful
life; and charging the main battery pack preferentially before
charging the supplemental battery pack. The method maintains the
useful life of the main battery pack as equivalent to an EV driving
life of at least 100,000 miles. The chemistry type of the main
battery pack is different from the chemistry type of the
supplemental battery pack. The preferential charging the main
battery pack occurs if the state of charge of the main battery pack
is less than a full charge, regardless of the state of the
supplemental battery pack. Some exceptions apply, e.g., when
charging the main battery pack is unsafe. The battery design of the
MBP and the SBP are different in terms of their ratings of: a
thermal profile rating, a cell impedance rating, an energy density
rating, or a cycle rating. The main battery pack has a cycle rating
that is greater than a cycle rating of the supplemental battery
pack, with ranges provided hereinabove.
[0056] The main battery pack and the supplemental battery pack can
be discharged sequentially. This can be accomplished by selecting a
discharge percentage for the main battery pack in a range of 50 to
90 percent; and discharging the main battery pack to the selected
discharge percentage prior to starting to discharge the
supplemental battery. Other percentage ranges can apply, such as
fully discharging the MBP. The preferential charging of the main
battery pack from a regenerative energy source occurs before
recharging the supplemental battery pack from the regenerative
energy source. One sequence of discharging/charging includes:
discharging the main battery pack to an approximately depleted
state; then discharging the supplemental battery pack; and charging
the main battery pack via a regenerative energy source
preferentially over the supplemental battery pack; and repeating
the discharging of the main battery pack to between 50-95 percent
of an original capacity prior to repeating the discharging of the
supplemental battery pack. An alternative discharge/charge sequence
is to: fully discharge the main battery pack to an approximately
zero charge; and then fully discharge the supplemental battery pack
to an approximately zero charge. The MBP is discharged more
frequently than the SBP in the present embodiment. The MBP and SBP
can be configured such that the useful life of the MBP and the
useful life of the SBP are equivalent to an EV driving life of at
least 100,000 miles. This is done by configuring the MBP to be
fully dischargeable to an approximately zero charge a number of
times over its useful life approximately equal to a cycle rating of
the main battery pack; and the supplemental battery pack can be
configured to be fully dischargeable to an approximately zero
charge a number of times over its useful life approximately equal
to a cycle rating of the supplemental battery pack. The number of
times the main battery pack is fully dischargeable divided by the
number of times the supplemental battery pack is fully
dischargeable results in a discharge ratio that is approximately
equal to a cycling ratio. Overall, the MBP and the SBP are
configured to be fully dischargeable while maintaining a lifetime
cycling of the battery subsystem of approximately equivalent to an
EV driving life of at least 100,000 miles.
Modeling Results and Conclusions
[0057] Below are several tables that provide five exemplary battery
combinations to illustrate the potential savings of the present
disclosure over existing battery architectures and discharge/charge
algorithms.
[0058] Target vehicle 1 (as it is a production car from a large
automobile manufacturer) is a real world reference. The stated
range is: 82 miles for a 20 kWh pack. This car has a 100 kW motor,
and weighs 3,300 lb. It is a 4 seater small sedan. Vehicle 2 is
similar but the stated range is: 73 miles for a 24 kWh pack, uses a
80 kW motor and weighs 3,400 lb. It is a 4 seater small sedan.
TABLE-US-00001 TABLE 1 This shows the key attributes of the chosen
cells from which the packs will be designed. Note there are 3 LTO
cells types and 2 Hi-Energy cell types. Key Battery attributes LTO1
LTO2 LTO3 LiCo LiS Voltage (V) 2.3 2.3 2.3 3.6 2.2 Max Voltage (V)
2.7 2.7 2.7 3.9 2.4 Min Voltage (V) 2.0 2.0 1.5 2.5 2.0 capacity
(Ah) 13.4 64.0 20 3.1 2.5 std charge (A) 13.0 50.0 20 1.7 fast
charge (A) 130.0 360.0 160 3.1 0.5 std discharge (A) 13.0 50.0 20
3.1 fast discharge (A) 130.0 360.0 160 6.2 5.0 pulse discharge
260.0 600.0 300 12.0 10.0 (A) weight (kg) 0.40 1.84 0.53 0.05 0.02
impedance 1.50 0.40 1.10 55.00 25.00 (mOhm) size (l) 0.20 0.84 0.26
0.03 0.02 std charge (C) 1.0 1.0 1.0 0.5 fast charge (C) 10.0 6.0
8.0 1.0 0.2 std discharge (C) 1.0 1.0 1.0 1.0 fast discharge (C)
10.0 6.0 8.0 2.0 2.0 Typ energy (Wh) 29 116 46 11 Peak power (W)
670 1,250 170 Specific Energy - 73 77 86 248 350 Wh/kg Energy
Density- 137 168 177 675 320 Wh/l Specific Power - 1,675 1,333 465
W/kg Power Density- 3,182 2,916 656 W/l Cycle life 16,000 16,000
4,000 250 400
[0059] Referring to Table 2 below, the chosen combinations of cells
in series to achieve the target voltage, and in parallel to achieve
the target current. A secondary objective is to achieve the
capacity required to meet the range of the vehicle when the two
packs are combined. Here the first objective is to size P1, the
main battery pack, so that approx 35-40 miles is possible,
targeting a daily commute, and then P2, the supplemental battery
pack, is sized to meet the target range. Note how LTO3 is the pack
in the reference vehicle 1, and so all range variations are
referenced from this vehicle. The key values derived here are in
turn used in the following table to design the dual chemistry
pack.
TABLE-US-00002 TABLE 2 Pack configurations for Target Vehicle:
100-mile range, 100 kW motor, Motor voltage range 400-260 V, life -
10 yr or 100,000 miles LTO1 LTO2 LTO3 LiCo LiS Max cells in series
148 148 173 104 167 Min cells in series 130 130 148 103 130 Max
Power (W) 104,000 240,000 120,000 4,800 4,000 Min Power (W) 67,600
156,000 78,000 3,120 2,600 Min Energy Capacity (Wh) 4,007 19,136
7,973 1,161 699 Cells in parallel for 100 kW 1 1 1 21 25 New min
capacity (Wh) 4,007 19,136 7,973 24,373 17,469 Min Pack size
multiplier 2 1 1 1 1 max power (W) 208,000 240,000 120,000 100,800
100,000 min power (W) 135,200 156,000 78,000 65,520 65,000 min
capacity Wh 8,013 19,136 7,973 24,373 17,469 min Weight (kg) 104
239 92 105 52 Total Pack Weight (kg) 155 357 137 233 116 Total Cell
Volume (liters) 52 109 45 74 75 Pack volume (liters) 80 168 69 165
166 Current/string (Amps) 83.6 167.2 125.4 6.4 7.2 lost
power/string (W) 1,363.2 1,454.1 2,999.1 231.3 166.4 losses @ 50 kW
5.5% 2.9% 6.0% 9.7% 8.3% Miles/kWh 4.1894 4.6068 4.1000 3.4903
3.7192 Range (miles) 33.6 88.2 32.7 85.1 65.0 Range/eff Factor
4
TABLE-US-00003 TABLE 3 Pack Combinations Pack combinations A B C D
E LTO1 + LTO1 + LTO2 + LTO2 + LTO3 + F G LiS LiCo LiS LiCo LiS Veh1
Veh2 Weight (kg) 271 388 473 590 253 344 300 Capacity (kWh) 25.5
32.4 36.6 43.5 25.4 20 24 range (miles) 102.6 127.2 160.9 186.8
101.0 82 73 max power P1 (W) 182,520 182,520 210,600 210,600
140,400 100,000 80,000 max power P2 (W) 78,000 102,211 78,000
101,400 78,000 Life P1 (years)** 51 51 131 131 12.8 26 10 Life P2
(years)** 16 13 11 Volume (L) 246 245 335 333 235 172 918 Pack
Wh/kg 94 83 77 74 101 58 Pack Wh/l 104 132 109 130 108 116 Ratio
P2:P1 2.2 3.0 0.9 1.3 2.2 100% m/kWh 4.0 3.9 4.4 4.3 4.0 4.1 3.0
Typical m/kWh 4.2 4.2 4.6 4.6 4.1 Est. pack cost ($)* $16,748
$20,200 $27,870 $31,323 $16,708 $20,000 $18,000 Range/pack weight
0.38 0.33 0.34 0.32 0.40 0.24 0.24 Range/pack cost 0.0061 0.0063
0.0058 0.0060 0.0060 0.0041 0.0041 $/kWh $657 $624 $761 $720 $657
$1,000 $750 **Life: Assume 40 miles/day, 6 days/week = 12,480
miles/year *Cost: Assume P1(LTO) = $1000/kWh, and P2(Hi En) is
$500/kWh
[0060] For reference, published data is shown for vehicle 1 & 2
(F & G) are single chemistry packs. The other packs are all
dual chemistry. The stated costs numbers are based on input from
vendors and research for both LTO cells and the LiCo and LiS cell.
Furthermore, the LiS cell is not yet in mass production but does
serve as a good indicator of battery types that may be available
shortly. The last 3 rows show normalized range by cost or weight of
the pack, and cost per kWh. These ratios are the best indicators of
which packs perform the best. Pack A/B/E makes the best option:
Smaller LTO and high-energy combination.
[0061] Pack `A` will not meet max power need from P2 but can be
mitigated as described above. However, it is the lowest cost pack
and most closely achieves the 100-mile specification.
[0062] Pack `B` will meet power need from P1 or P2 but has a larger
more expensive pack, which exceeds the range spec. However, this
pack has the best range normalized for either cost or weight.
Therefore, this pack is the best choice to meet the target
specification.
[0063] `E` will also not meet max power from P2 alone, but has the
highest range normalized by weight since both LTO3 and LiS cells
have the best energy density by weight.
[0064] As expected the single packs (F&G) have the worst range
performance numbers. Another important item to bear in mind is the
ratio of P2:P1. Typically P1 (LTO) should be smaller by a ratio of
somewhere between 3:1 to 5:1, and larger packs can have a higher
ratio (Higher percentage of hi-energy, low cost battery) which will
make the total pack lower in cost and weight.
CONCLUSIONS
TABLE-US-00004 [0065] TABLE 4 Comparison Comparison W X Y Z B vs.
Veh1 B vs. Veh2 E vs. Veh1 A vs. Veh2 Range 155% 174% 123% 125%
weight 113% 129% 73% 79% cost 101% 112% 84% 84% volume 142% 27%
137% 143% Capacity 162% 135% 127% 127% Range/cost 154% 155% 147%
149% Range/weight 137% 135% 168% 159%
[0066] With packs A/B/E vs. the single pack, there is an approx 50%
advantage in range when cost is fixed or weight is fixed. This is
indeed the most important conclusion and most compelling deduction
from this analysis.
[0067] The present invention is well suited to using different
combinations of different battery types including: sodium-ion,
lithium sulfur, Lithium manganese oxide, lithium iron phosphate,
lithium manganese spinel, etc.
Implementations
[0068] Methods and operations described herein can be in different
sequences than the exemplary ones described herein, e.g., in a
different order. Thus, one or more additional new operations may be
inserted within the existing operations or one or more operations
may be abbreviated or eliminated, according to a given
application.
[0069] Other features of the present embodiments will be apparent
from the accompanying drawings and from the detailed description.
In addition, it will be appreciated that the various operations,
processes, and methods disclosed herein may be carried out, at
least in part, by processors and/or electrical user interface
controls under the control of computer readable and computer
executable instructions stored on a computer-usable storage medium.
The computer readable and computer executable instructions reside,
for example, in data storage features such as computer usable
volatile and non-volatile memory and are non-transitory. However,
the non-transitory computer readable and computer executable
instructions may reside in any type of computer-usable storage
medium.
[0070] The foregoing descriptions of specific embodiments of the
present disclosure have been presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Many modifications
and variations are possible in light of the above teaching without
departing from the broader spirit and scope of the various
embodiments. The embodiments were chosen and described in order to
explain the saliently significant principles of the invention and
its practical application in the best way, and to enable others
skilled in the art to best utilize the invention and various
embodiments with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the Claims appended hereto and their
equivalents.
* * * * *